Electrochemical corrosion parameters for active and passive reinforcing steel in carbonated and sound concrete

The electrochemical corrosion parameters, such as corrosion potential, corrosion current density, and the Tafel constants are necessary inputs for the corrosion modeling in reinforced concrete. Literature shows large variability in their values, whereas the data are scarce for the carbonated concrete. This paper presents a range of corrosion parameters for the active steel in carbonated and the passive steel in noncarbonated concrete. Forty-eight singly reinforced concrete cylinders were cast, of which 24 were carbonated and the others were sound samples. Potentiodynamic polarization curves were obtained at three different scan rates and extrapolated to extract the corrosion parameters. To validate these parameters, a macrocell corrosion system was simulated using FEM-based Comsol multiphysics® software. The numerical results were compared to two experimental studies. A natural dispersion in the values of corrosion parameters for both active and passive steels was observed. The average Stern–Geary constant was 54 and 47 mV for active and passive steels, respectively. Numerical simulations with the obtained parameters predicted the macrocell corrosion in partially carbonated concrete with a high accuracy. The presented values of corrosion parameters in this study could help researchers and engineers to simulate the corrosion phenomena in concrete accurately.     

Novel amphiphilic conetworks based on compatibilized NBR/SBR–montmorillonite nanovulcanizates as membranes for dehydrative pervaporation of water–butanol mixtures

Nanocomposite vulcanizates comprising the poorly compatible acrylonitrile butadiene rubber/styrene butadiene rubber blend are homogenized with 20 parts per hundred montmorillonite forms showing various levels of amphiphathicity: slightly hydrophobic (Mont‐25/50) and highly hydrophobic (Mont75/100) as compared to the highly hydrophilic pristine form (Mont‐0). The purpose of the amphiphathicity is to afford simultaneous binding sites for the poorly compatible components. Thus maximum compatibility is reached with either Mont‐75 or Mont‐50 which improves the mechanical properties. Scanning electron microscopy corroborates cocontinuous morphology. Water vapor permeation through sheets/membranes fabricated from these compositions follows best performance with Mont‐25 followed by Mont‐50 while Mont‐75 and Mont‐100 based membranes acquire an organized continuous drop. This highlights the role of organophilicity in dominating the morphology and performance in pervaporation application. Dehydration of butanol is effective using such membranes with superiority for Mont‐25 based membrane. A plausible model for the transport mechanism was proposed and supported by activation energy calculations for the permeation of the individual components and the sorption affinity measurements as well. All these parameters together suggest the arrest of the n‐butanol within the macrmolecular chains of the membranes, favored by its chemical affinity. This allows therefore a passageway for the water to cross to the other side of the membrane through plasticization of the chains and creation of free volumes which is known as solution diffusion mechanism. POLYM. ENG. SCI., 54:1560–1570, 2014. © 2013 Society of Plastics Engineers     

Brain functional localization: a survey of image registration techniques

Functional localization is a concept which involves the application of a sequence of geometrical and statistical image processing operations in order to define the location of brain activity or to produce functional/parametric maps with respect to the brain structure or anatomy. Considering that functional brain images do not normally convey detailed structural information and, thus, do not present an anatomically specific localization of functional activity, various image registration techniques are introduced in the literature for the purpose of mapping functional activity into an anatomical image or a brain atlas. The problems addressed by these techniques differ depending on the application and the type of analysis, i.e., single-subject versus group analysis. Functional to anatomical brain image registration is the core part of functional localization in most applications and is accompanied by intersubject and subject-to-atlas registration for group analysis studies. Cortical surface registration and automatic brain labeling are some of the other tools towards establishing a fully automatic functional localization procedure. While several previous survey papers have reviewed and classified general-purpose medical image registration techniques, this paper provides an overview of brain functional localization along with a survey and classification of the image registration techniques related to this problem.     

An integrated framework for wireless sensor network management

Wireless sensor networks (WSNs) have significant potential in many application domains, ranging from precision agriculture and animal welfare to home and office automation. Although sensor network deployments have only begun to appear, the industry still awaits the maturing of this technology to realize its full benefits. The main constraints to large‐scale commercial adoption of WSN have been the lack of available network management and control tools, such as for determining the degree of data aggregation prior to transforming it into useful information, localizing the sensors accurately so that timely emergency actions can be taken at an exact location, routing data by reducing sensor energy consumption, and scheduling data packets so that data are sent according to their priority and fairness. Moreover, to the best of our knowledge, no integrated network management solution comprising efficient localization, data scheduling, routing, and data aggregation approaches exists in the literature for a large‐scale WSN. Thus, we introduce an integrated network management framework comprising sensor localization, routing, data scheduling, and data aggregation for a large‐scale WSN. Experimental results show that the proposed framework outperforms an existing approach that comprises only localization and routing protocols in terms of localization energy consumption, localization error, end‐to‐end delay, packet loss ratio, and network energy consumption. Moreover, the proposed WSN management framework has potential in building a future “Internet of Things”. Copyright © 2012 John Wiley & Sons, Ltd.     

Molecular identification and pectate lyase production by Bacillus strains involved in cocoa fermentation

We have previously reported the implication of Bacillus in the production of pectinolytic enzymes during cocoa fermentation. The objective of this work was to identify the Bacillus strains isolated from cocoa fermentation and study their ability to produce pectate lyase (PL) in various growth conditions. Ninety-eight strains were analyzed by Amplified Ribosomal DNA Restriction Analysis (ARDRA). Four different banding patterns were obtained leading to the clustering of the bacterial isolates into 4 distinct ARDRA groups. A subset of representative isolates for each group was identified by 16S rRNA gene partial sequencing. Six species were identified: Bacillus subtilis, Bacillus pumilus, Bacillus sphaericus, Bacillus cereus, Bacillus thuringiensis, together with Bacillus fusiformis which was isolated for the first time from cocoa fermentation. The best PL producers, yielding at least 9 U/mg of bacterial dry weight, belonged to B. fusiformis, B. subtilis, and B. pumilus species while those belonging to B. sphaericus, B. cereus and B. thuringiensis generally showed a low level of activity. Two kinds of PL were produced, as revealed by isoelectrofocusing: one with a pI of 9.8 produced by B. subtilis and B. fusiformis, the other with a pI of 10.5 was produced by B. pumilus. Strains yielded about 2 fold more PL in a pectic compound medium than in glucose medium and maximum enzyme production occurred in the late stationary bacterial growth phase. Together all these results indicate that PL production in the bacilli studied is modulated by the growth phase and by the carbon source present in the medium.     

Phosphorylation of starch and dextrin by dry‐heating in the presence of phosphate,and their calcium phosphate‐solubilizing ability

Starch and dextrin were phosphorylated by dry‐heating in the presence of phosphate, and their properties were examined. The phosphorylation of starch was accelerated with decreasing moisture, rising incubation temperature and prolongation of the incubation period. However, a rise in incubation temperature, and lengthened incubation period caused increased browning and degradation. A decrease in the pH from 5.5 to 3.0 resulted in a modest increase of phosphorylation, but also marked browning and degradation. When potato starch was phosphorylated at 140°C and pH 5.5 for 24 h, its phosphorus content was increased up to 3.47%, with fewer side reactions. Phosphorlylated starch and dextrin had calcium phosphate‐solubilizing abitity. Phosphorylated dextrin with 2.42% phosphorus had about half the calcium phosphate‐solubilizing ability of casein phosphopeptide (CPP). The possibility of substituting of phosphorylated starch and dextrin for CPP as a calcium phosphate‐absorption enhancing material is discussed herein.     

NO Relaxation Approach (NORA) to predict thermal NO in combustion chambers

In combustion models employing tabulated or global kinetics, the prediction of thermal NO is usually performed by either the direct resolution of Zel’dovich mechanism or the tabulation of the NO reaction rate using a laminar flamelet database and a progress variable representative of the fuel oxidation reactions, for instance temperature or a linear combination of major products mass fractions. It is known that the first method lacks accuracy if radical species such as N or O appearing in the NO reaction rate are not correctly estimated. The second method cannot lead to accurate predictions because NO reactions take place essentially when the fuel oxidation is over, therefore the NO reaction rate shows a very weak correlation with the progress variable. In this paper a new approach called NO Relaxation Approach (NORA), is proposed for the modeling of thermal NO. It allows a high accuracy when coupled with this type of combustion models. With NORA, the NO reaction rate is written as a linear relaxation towards the equilibrium value with a characteristic time τ. Both parameters are tabulated as functions of equivalence ratio, pressure, temperature and dilution mass fraction. NORA is first validated on homogeneous internal combustion engine cases, where it closely fits the complex chemistry results. It is then integrated into the turbulent combustion model ECFM3Z dedicated to piston engine applications. In this model a mixed tabulated (TKI) and global kinetics (CORK) approach is used to describe turbulent combustion. First applications on eight Diesel engine operating points show a good improvement with NORA compared to a classical resolution of Zel’dovich mechanism.     

Shear strength of geosynthetic composite systems for design of landfill liner and cover slopes

Torsional ring shear tests were performed on composite specimens that simulate the field alignment of municipal solid waste (MSW) landfill liner and cover system components. Simultaneous shearing was provided to each test specimen without forcing failure to occur through a pre-determined plane. Composite liner specimens consisted of a textured geomembrane (GM) underlain by a needle-punched geosynthetic clay liner (GCL) which in turn underlain by a compacted silty clay. Hydrated specimens were sheared at eleven different normal stress levels. Test results revealed that shear strength of the composite liner system can be controlled by different failure modes depending on the magnitude of normal stress and the comparative values of the GCL interface and internal shear strength. Failure following these modes may result in a bilinear or trilinear peak strength envelope and a corresponding stepped residual strength envelope. Composite cover specimens that comprised textured GM placed on unreinforced smooth GM-backed GCL resting on compacted sand were sheared at five different GCL hydration conditions and a normal stress that is usually imposed on MSW landfill cover geosynthetic components. Test results showed that increasing the GCL hydration moves the shearing plane from the GCL smooth GM backing/sand interface to that of the textured GM/hydrated bentonite. Effects of these interactive shear strength behaviors of composite liner and cover system components on the possibility of developing progressive failure in landfill slopes were discussed. Recommendations for designing landfill geosynthetic-lined slopes were subsequently given. Three-dimensional stability analysis of well-documented case history of failed composite system slope was presented to support the introduced results and recommendations.